A notice of proposed rulemaking has been issued by U.S. DOT that may require one or more of several additional measures to protect aircraft against lithium battery fires. It is expected to become law in 2012. The new law may have a short time of compliance, in fact the proposed rule states the time of compliance will be only seventy-five days.
There is a need for air freight carriers to convert their lower deck cargo compartments of their airplanes to Class C compartments by providing them with a FAA approved smoke detection and fire suppression system. In addition, many air freight carriers seek an alternative solution that is capable of providing fire protection everywhere in the cargo compartments of their air carrier aircraft fleet. Obviously, everywhere includes in the main cargo area as well as in the lower lobe cargo compartments. In all of these cargo compartments may be Unit Load Devices (ULDs) and pallets—which can be covered with blankets or nets, hereinafter all referred to as “ULDs.”
It would therefore be beneficial to have a traditional fire suppression system (“FPS”) for the lower deck cargo compartments, and an additional solution to be used in conjunction or separately with the traditional (i.e. Halon) FPS used on these aircraft.
Earlier fire suppression devices often employ gaseous, liquid, or water-based foam products that are released into the cargo hold or individual freight containers (ULDs for example), and are usually intended to: 1) cover the burning cargo inside the ULD and create an oxygen-depriving medium (for example a foam system used and owned by Federal Express), 2) create an inert atmosphere inside the ULD, as with the Vulcan or Halon/Halon Replacement gaseous extinguishing systems, 3) create a cooling medium, such as provided by water misting technology, or 4) retard a fire's propagation.
As applied to cargo carried on aircraft, the earlier methods relied upon the ULD containing a foam, gas, protected structure, or water-mist system. Some agents proposed in earlier methods have properties which are toxic, corrosive, subject to freezing, have short-lived durations of protection (usually due to the inability of the ULD to sufficiently overcome leakage) or have a combination of these characteristics, all detracting from a reliable and simple method of controlling fires likely to occur today in a ULD.
Most early foam suppression systems operate on the principle that oxygen deprivation or suffocating the fire is sufficient to extinguish a fire. There are cases, however, where a fire is too strong and oxygen deprivation and suffocation simply is not enough. In addition, once depressurization of the aircraft occurs the necessary amount of foam or gas mixture may leak out, or be forced out, of the aircraft and therefore not sufficiently extinguish the fire; and/or when the aircraft descends the air density inside will again be sufficient to support a fire. Accordingly, there is a need in the art to provide oxygen deprivation but offer a system that will, in addition, substantially seal off the fire and fight the fire through char formation and/or intumescence chemical action.
Earlier fire suppression systems generally employ a means within or from the ULD's to interface with the aircraft systems and/or the operational personnel. Some early fire suppression systems provide merely a means to warn the crew of a fire and others allow the crew some control the ULDs fire suppression device and the response of the related fire suppression systems.
None of the earlier crew interface means provide protection of the interface device that detects the fire and communicates with the crew from explosions and projectiles capable of damaging the interface device; thus, preventing the interface means from performing its intended functions. Therefore, there is a need in the art to provide a fire suppression system that is protected against explosions and projectiles.
Moreover, weight, volume, and the cost to maintain products in airworthy condition are all critical in air freight operations. Earlier proposed fire suppression systems included adding the fire suppression means in all of the ULDs or throughout the aircraft itself. In other words, a built-in solution. However, these proposed systems are not optimal because they add unnecessary weight to the overall load of the air freight plane because the additional fire protection may not be needed for all freight depending on type. The proposed earlier fire suppression systems add about sixty (60) pounds to each ULD carried by the air freight planes used. Thus, there is a need in the art for a fire suppression system that weighs less than sixty (60) pounds, and/or can be selectively placed in ULD's that pose an increased risk of a fire not suppressible with standard fire suppression systems. Further, there are also no standards or practices to determine, before each use, the airworthiness of a ULD with such added fire suppression means.
Built-in systems also pose cost and reliability concerns. The costs to develop, certify, and maintain built-in systems are often substantial. The reliability of some of these devices and/or built-in systems is unknown unless developed and analyzed simultaneously with a proper Safety Assessment.
ULDs are typically subject to very rough treatment and storage conditions. To Applicant's knowledge, there are currently no discussions, procedures, or instructions to evaluate ULD normal wear and tear on the ability of the means to perform its intended function. There are no standards directed to repair and service of ULDs or about the minimum equipment list (MEL) dispatch requirements for a fire suppression means, the ULDs, or aircraft containing the ULDs and the fire suppression means. Fires are not likely to occur outside of the ULDs located in the main and lower lobe compartments because the freight is only located in these ULD containers. Thus, the source of a fire is most likely to be the freight inside of the ULD, and often the risk may be limited to only a few ULDs on each carrier that contain materials, such as lithium batteries, that pose substantial and unique fire threats.
Similar, pallets or boxes in trailers of one of the millions of over-the-road tractors may include materials that pose a fire risk. Thus, there is a need in the art for a fire suppression system that can be configured to be installed in the trailers of semi-trucks to protect the cargo and contents of the trailer. Further, as more and more cars and trucks are being offered with a hybrid or all electronic drive systems, there is a concern of the battery bundles being ignited and burning after a crash, a particular shortcoming has been observed in side impact collisions. Once the lithium (or other long range) batteries are exposed or broken, there is the chance of spontaneous ignition and the fires of these metals are very difficult to extinguish. Thus, there is a need in the art for a fire suppression system that can adequately contain and extinguish such a fire in over-the-road trailers and the battery enclosures of hybrid or electric cars.
There are three (3) phases of a fire—the incipient phase, the visible smoke phase, and the heat and flame phase. The most reliable and effective fire protection systems are those which deploy in the early phases of a fire. Otherwise, a fire is much more difficult to bring under control and it causes much more damage once the fire is in the heat and flame phase.
Since depressurizing the cargo compartment(s) of a freighter aircraft is one traditional means to suppress a fire, the traditional fire suppression system (Halon) cannot be activated until after these compartments are depressurized. Otherwise, if the traditional fire suppression system is first deployed the extinguishing agent will be forced out of the airplane and what agent remains, if any, will be too diluted to be effective. Thus, there is an exposure to a growing fire during the time to depressurize the aircraft and for the aircraft to reach a cabin altitude where there is insufficient oxygen to support a fire.